Work-in-circuit arc starting apparatus



March 4, 1969 Af MANZ 3,431,390

WQRK-IN-CIRCUIT ARC STARTING APPARATUS Filed May 20. 1965 DC. ANon-Consumable POWER SOURCE Material INVENTOR AUGUST F. MANZ Jamaal $457ATTORN United States Patent 3,431,390 WORK-IN-CIRCUIT ARC STARTINGAPPARATUS August F. Manz, Union, N.J., assignor to Union CarbideCorporation, a corporation of New York Filed May 20, 1965, Ser. No.457,388 US. Cl. 219-130 6 Claims Int. Cl. B23k 9/00, 9/10 ABSTRACT OFTHE DISCLOSURE This invention provides for improving main arc startmg byincorporating into the torch a substantially electrically non-conductivegas cup which is located about the electrode, the cup comprising bothnonconductive and conductive material and being directly grounded to thework lfor inhibiting undesirable are starting blocking potentia Thisinvention relates to work-in-circuit are starting apparatus, and moreparticularly, to non-consumable electrode-inert gas shielded arcwelding.

The invention provides for improving main arc starting by making thesubstantially electrically non-conductive gas nozzle or cup at leastpartially electrically conductive and grounding the latter to the work,so that undesirable blocking potential is prevented from accumulating onthe cup, thus assuring starting of the are even with high frequency.

Prior to the invention, the use of high frequency in starting the mainarc presented a problem in that the arc occasionally failed to start.

The main object of this invention is to solve such problems by simpleand economical means.

This object is accomplished either by coating a cup that is composed ofrelatively electrically non-conductive material with material that isconductive, or by providing a cup that is composed of a combination ofconductive material as well as non-conductive material, and electricallyconnecting such conductive material on or in the cup to the work to bewelded, by an auxiliary circuit. This bleeds undesirable arc blockingpotential from the cup and results in more reliable starting of the mainarc.

In the drawing:

FIGURE 1 is a circuit diagram of apparatus illustrative of theinvention; and' FIGURES 2 and 3 are enlarged sections of modificationsof the cup.

As shown in such drawing, a torch 10 comprising a tungsten electrode 12and a gas cup 14 is located above the work 16 to be welded in the usualway. Such electrode is connected by lead 18 to a power source 20 that isprovided with high-frequency are starting means. The other terminal ofsuch source 20 is connected to the work 16 by a ground lead 22. Inertgas, such as argon 24, is supplied to the torch 10 and flows through cup14 to protect the operation from the atmosphere.

The cup 10, FIGURE 2, is composed of material 26 that is substantiallyelectrically non-conductive, such as alumina, having an annular coating28 composed of electrically conductive material, such as graphite. Suchcoating 28 is connected to the work 16 by a pigtail conductor 30 that isheld by place at one end on the cup by a spring clip, not shown.

In operation, the coating 28 and conductor 30 act to bleed from the cupany electrical charge which tends to accumulate thereon to the workwhile also acting as a relatively high impedance to the main are,thereby preventing any undesirable main arc current from flowingtherethrough.

Thus, even with the aid of high frequency to start the main are betweenthe electrode 12 and work 16 in the inert gas stream, undesirable arestarting blocking potential buildup on the cup is inhibited, assuringmore reliable starting of the main are, even under repetitive startingconditions.

As shown in FIGURE 3, the cup 10a is made by mixing conductive material,such as graphite, or metal, in the form of powder with the aluminapowder of the cup, before molding and baking the latter. Thus, the cupcontains conductive as well as non-conductive material, and is groundedto the work as pointed out above for the same purpose.

What is claimed is:

1. A non-consumable electrode gas shielded are working system comprisinga torch, the electrode of which is connected in circuit with an arcenergizing power source, and the Work, which power source includeselectrical means for starting such arc, said torch being provided with asubstantially electrically non-conductive cup surrounding said electrodefor directing the gas about such arc to shield the operation from theatmosphere, said cup being directly grounded to said work for inhibitingundesirable are starting blocking potential.

2. A system as defined by claim 1, in which said are starting meanscomprises high frequency.

3. A system defined by claim 1, in which said cup comprises anon-conductive core and a coating of conductive material.

4. A system as defined by claim 3, in which said core comprises aceramic.

5. A gas cup for non-consumable electrode inert gas shielded arctorches, consisting of a composite material of a substantiallyhomogeneous mixture of electrically conductive particles andelectrically non-conductive particles.

6. A gas cup as defined by claim 5, in which the nonconductive particlescomprises a ceramic.

References Cited UNITED STATES PATENTS 2,620,422 12/1952 Volfi 219-2,992,320 7/1961 Hill 21975 2,922,023 1/ 1960 Hackman et al 219-l27RICHARD M. WOOD, Primary Examiner.

J. GREGORY SMITH, Assistant Examiner.

U.S. Cl. X.R. 219

